Great ProductBy Troyon 10/30/2013

Troy would recommend this product to a friend

I have only used a couple of ATO systems and this is far superior to others. It's well worth the extra money. My previous ATO used dual float switches that would calcify or be affected by turbulence in the sump. This is spot on every time. I have a larger system 300 gallons so the pump being able to run for an extended amount of time is great. I also like that the pump will automatically turn itself off after a certain amount of time as another added precaution

Great Quality!By Jorgeon 9/8/2013

Jorge would recommend this product to a friend

I have to say that this system has made my life much better! I don't have to worry about adding fresh RO/DI water every other day due to evaporation, it keeps my water at the perfect level and creates a much more stable environment for my fish.

The system was incredibly easy to install and it works perfectly. This will be the only top off system I will use on future tanks.

If you need a top off system... buy this unit and don't compromise on anything else!

Great Reliable ProductBy Ryanon 8/25/2013

Ryan would recommend this product to a friend

Best ATO in my opinion, very accurate and simple to set up. The initial set up was easy but had a little trouble with bubbles covering the optical sensor causing it to overflow and make the float valve go off. I turned it off and let it sit in the water for a few hours, then plugged it in and has worked ever since.

A little spend, but a crucial part of the aquarium

A good product that could use a little refining.By Matton 8/15/2013

Matt would recommend this product to a friend

Overall I found this product easy to set up and install. Once properly set up, this has kept the water levels in my sump very stable.

I do have a couple of small complaints though:
1) I wish the instructions had come right out and said to place the primary sensor in an area of the sump with NO, and I mean NO, air bubbles rather than telling you that in the trouble shooting section.
2) A better mounting system for the controller. A couple of stick on pieces of Velcro? A simple mounting bracket or even molded screw holes would be better.
3) The LED indicators are unshielded and impossible to read unless you are looking at the controller straight on.

Honestly, where is the much hyped "German quality and attention to detail?" For $200+, I would think Tunze could do better.

Best ATO money can buyBy Joeon 8/12/2013

Joe would recommend this product to a friend

Great product. Exceed expectations. Even though it's a little pricey but it does come with the pump so that make it reasonable. Very acurrate and trustworthy. I expect it to work a long time.

Quality productBy Salon 7/21/2013

Sal would recommend this product to a friend

This was very fun and simple to install. It works flawlessly.

Reliable and effective By Andrewon 7/20/2013

Andrew would recommend this product to a friend

I have had this running a few months on my 80 gallon reef. The unit was relatively easy to set up, the instructions are just poorly laid out. Once set up there were no issues and it has been keeping my water level consistent.

Well worth the price!!!!!!!!!!!By jhmeresquon 7/8/2013

jhmeresqu would recommend this product to a friend

I utilized it as my ATO for my RO/DI water return to sump system to replace evaporated water. Works great , love the fact that it has the Sensor Eye and the backup float switch. Can't get enough redundancy. A little pricey but well worth it.

Great investmentBy Mpekon 6/30/2013

Mpek would recommend this product to a friend

All I have to say is that this system makes my life a lot easier! As long as I keep my ATO container full it runs flawlessly. I would recommend this to anyone.

Not bad By Shalashaskaon 6/28/2013

Shalashaska would recommend this product to a friend

I've had it so far for 3 days. The set up was easy. I dident have to use the instructions what so ever. The only thing I found so far that is a issue is that micro-bubbles from my protein skimmer like to settle on the optical eye, thus giving a false water low indication. I just moved it to a better location, problem solved.

Great But there is a break in period.By Willon 6/26/2013

Will would recommend this product to a friend

So for the first 3 or 4 days the "eye" sensor has a hydrophobic film which will make the sensor think it is in the air and will continuously pump water until the float switch will shut it off I recommend you leave the sensor in the sump for 2-3 without turning it on that will resolve these issues.

Overall nice ATOBy PMKon 6/17/2013

PMK would recommend this product to a friend

I am pleased with this ato unit. I had some issues with the pump just kicking on and staying on. Dropped 2L of rodi into the system and stopped when the float kicked in. I couldn't figure it out and thought I might have a bad unit. So broke it down off my display and set it up on my mixing tank. The same thing happened. So ran through the set up again and disconnected the pump from the power supply wires and connected them up again. That did it. The pump no longer kicks in and stays on. Haven't seen this in other reviews or the Tube but did see a review about a weird first hour break in period. Guess it was the connection or the break in period. But its been on my display for a couple weeks now and has kept the water level very stable. Been monitoring the salinity and everything has been real stable. I think it will be a long term success. I agree with some other reviews that it seems a bit delicate for a couple hundred bucks.

Great Product!By Andyon 6/8/2013

Andy would recommend this product to a friend

I purchased this item about a year ago for my Red Sea Max 250. The skimmer on that tank is very finicky and needs constant adjustments to work properly when the water level changes. This ATO has fixed that issue for good! I have a five gallon bucket of RODI water sitting under the tank for top off purposes and the Osmolator takes care of the rest. My tank water level is always where it needs to be and my skimmer is running at optimum efficiency. If you're looking for a good quality and reliable ATO look no further!

Working great for the past 8 monthsBy Ronon 6/3/2013

Ron would recommend this product to a friend

Have had this ATO unit for almost 8 months on a 90 Gal reef with no issues. Working as good today as the day I got it. Set up was easy. No more having to add top off water every day.

Excellent Product, Well Worth the extra $$$By Huckon 5/31/2013

Huck would recommend this product to a friend

Initially, I was reluctant to spend the extra money on the Tunze. I did tons of research and I saw this product had excellent reviews, but what sealed the deal for me is, I was reading reviews on a JBJ auto top off system and someone who purchase a JBJ stated that he wish he would have went with the Tunze and not taken the cheaper option.
Unit has been in service now for approx 3 months and not a single problem. Definitely the way to go!

Top-notch !!!!!!!!!By Jimboon 5/30/2013

Jimbo would recommend this product to a friend

Sweet, could't ask for a better quality ATO system.Like the redundency with the Sensor and the float switch combined.
Excellent product. Worth the extra investment.

Works great when it is working, if you can figure it outBy tramboneplayer5on 5/18/2013

tramboneplayer5 would recommend this product to a friend

The instructions for this are terrible. For something that costs this much, I think they could have hired a better translator to write the instruction manual. After watching people on youtube and reading threads on reefcentral, I am pretty sure I have it all together, but the water line occasionally falls out of the pump and the pump will continue to run while shooting water up in the air. Be sure to have a lid on your water reservoir.

For $200, I don't get a finished product?By Mikeon 5/14/2013

Mike would recommend this product to a friend

I haven’t set it up yet and I’m sure it will work as advertised, but it contains a feature that is a pet peeve so excuse me while I rant a bit. The pump connects to the controller via two bare metal wires that have to be manually wired to a “terminal” connected to the controller. The manual does not explain how this is to be done. I got instructions from Tunze and had the strong impression that the rep thought I was either lazy or stupid for asking. I may be both, but when I pay more than $200 for an electrical product, I expect it to be fully wired. What would it have cost Tunze to add two snap in parts to connect the pump and the controller? A few pennies extra for each piece? So why didn’t they do it? I suspect because Tunze, like other major manufacturers of aquarium equipment, assumes that they can cut corners and the customers won’t complain. Well, it’s really no big deal, right? But what if you bought a top of the line coffee maker for $200 and it required that you wire the plug to make it work? Would that be ok? How about the numerous Chinese manufacturers who provide instructions for their product in absolutely incomprehensible English? I could go on. But if this kind of thing occurred in any other consumer market, there be an outroar. But since it’s just an aquarium product, we just shrug and look for a work around. IMO, we deserve better

good for a whileBy lwillis22on 5/14/2013

lwillis22 wouldn't recommend this product to a friend

I have had this product running on my 125 gallon tank and it has been a life saver. However, it started malfunctioning and I had to return it to Germany to get fixed or replaced. It cost me $35 to ship it there and that was the cheap route. It has been 1 1/2 months since I shipped it out and still no contact from them.

What a Great Product:By Bruceon 5/9/2013

Bruce would recommend this product to a friend

For anyone that wants peace of Mind about their aquarium, this is the product for you. An accurate, automatic device that will add DI water or Kalkwasser to your Sump is the way I use it. Perfect for the person that makes short trips, without the worry of evaporation causing your salinity levels to rise while your gone. A perfect 5 from Me.

A MUST for larger tanks with large evaporation rates!By RandoReeferon 5/7/2013

RandoReefer would recommend this product to a friend

After upgrading to a 125g tank with a 30g sump, I noticed my evaporation rate upgraded also. One week of manually topping off 1.5gal per DAY, was enough for me to pull the trigger on this ATO.

I really trust the sensor on this system! I was close to buying the JBJ Auto Top Off but I'm so glad I put up the extra money for this one. It is sleek, provides a variety of setup options, VERY Accurate, and easy to setup. I gave it 4.5 stars, because it could have used a few more directions or a FAQ section.

Why didnt i get one sooner!By Jasonon 5/1/2013

Jason would recommend this product to a friend

I finally made this purchase and its a life saver!
comes with everything needed (except water container).only issue is the
eye sensor gets micro bubbles on it when first installed which causes it to pump water continiuosly till high level alarm shuts it off.best advice is clean sensor with vinegar and let it sit in your sump for a couple days then its trouble free.

The best hands down.By Alexon 4/13/2013

Alex would recommend this product to a friend

Tunze osmolator top off is the best system you can buy. Well worth the price, comes with its own pump and has 2 different technologies working flawlessly to protect your tank and home from a flood.

great ATOBy illyaon 4/13/2013

illya would recommend this product to a friend

This is my second unit i'm ordering, first one was about 2 years ago. This is for a second setup, the first one is doing great. The one problem with these is the power plug. After sometime it becomes corroded and you get strange errors like overfill alarm wont stop. But if you have any problem the first thing to do is take off the 2 screws and clean the port and the plug. I cut a nail file down to about 1/8" to clean the port, and just a drill bit to scrape the plug inside. worked great and im good for another 6 months at least. At some point i'll just solder the wires and never deal with it again.

Worth every penny!!!By Stevenon 4/4/2013

Steven would recommend this product to a friend

You do get what you pay for... Keeps my water level constant. Love the optical sensor they use on this system. No brainier to install. Now all I need is to make something to hide the top off container...

awesome productBy brianon 4/4/2013

brian would recommend this product to a friend

I recently upgraded my 60 gallon reef tank to a 180 gallon. With my 60 I just topped off the old fashioned way but that was getting to be a chore with the new tank. I was on board with purchasing an auto top off but had serious concerns about failure...particularly in the on position. Virtually every other ato product out there was peppered with negative reviews regarding failure. We have thousands invested in the tank so it was worth it to spring for the osmolator. Piece of mind and very easy to setup. Skimmer works a lot better to.

AmazingBy Danon 3/27/2013

Dan would recommend this product to a friend

Probably one of the best investments I have made in this hobby. A really solid product.

Excellent productBy P Duffleson 3/25/2013

P Duffles would recommend this product to a friend

I'll simply agree with the multitude of people praising this ATO. This thing literally changed my life :D

The bestBy FISHYon 3/25/2013

FISHY would recommend this product to a friend

The best thing that you can do to your tank.

Good Top Off Bad InstructionsBy Mikeon 3/25/2013

Mike would recommend this product to a friend

The instructions on this top off could be WAY easier to understand if it didn't have 6 different languages on each page. Also, it should also state in there that you need to soak the opitcal sensor in soapy water and gently wipe off the polishing residue on the sensor before installation, also there is a dial on the inside of the controller that you need to set depending on the size of the aquarium or sump that you place the sensor in, the dial basically sets the dosing the pump pumps water into the tank/sump. A little better instructioni pamphlet would give this product 5 stars!

Great product!!By Bosleyon 3/15/2013

Bosley would recommend this product to a friend

I have this running on my aquarium and it is spot on and fail proof . the back up plunger has not been activated Probably because the top off system works so efficient, Great product recommend to anyone who is tired of adjusting or just having other systems that fail.

Not Cheap..you get what you pay forBy Curtison 3/10/2013

Curtis would recommend this product to a friend

Best ATO available

Love It!!!By Troyon 3/2/2013

Troy would recommend this product to a friend

You get what you pay for, and this ATO is awesome!!! Easy to setup and fail safe. Great quality.

Serious about reefing? Get this!By Chrison 2/27/2013

Chris would recommend this product to a friend

One of the smartest purchases I've made. Expensive but made with quality and plenty of mounting options. Highly recommend!

Worth the InvestmentBy JOHN on 2/24/2013

JOHN would recommend this product to a friend

I was a little apprehensive about spending this kind of money on an ATO. From the moment I opened the box I recognized the quality. Works perfect, provides piece of mind, and everything you need is included. Previously bought JBJ but was disappointed due to lack of redundancy. This should be fail proof with dual sensor/float valve.

Tunze ATOBy Toby Flendersonon 2/23/2013

Toby Flenderson would recommend this product to a friend

Pros: works perfectly, precisely, the German way.
Cons: hard to fight off all the ladies who want to get there hands on my tunze.

best topoff out thereBy chrison 2/18/2013

chris would recommend this product to a friend

This topoff is the best there is. I replaced my jbj with this and am so glad I did. The optical sensor with a float is pretty much fail safe and my water level stays the same.

Love it!By Joeon 2/13/2013

Joe would recommend this product to a friend

I've never had an ATO system, but this unit is awesome! I had no problems setting it up. Sure, the instructions MIGHT be lacking a little, but I don't feel the complaints below are justified.

The main sensor monitors the water level and activates the pump. The other one can be used as a safety shutoff/alarm OR as an alert that your ATO reservoir is empty.

It's your choice!! I, personally, set it up in the latter form and the product works great.

TerribleBy Pissedreeferon 2/1/2013

Pissedreefer wouldn't recommend this product to a friend

This product sucks end of story

Perfect!By Calvinon 1/15/2013

Calvin would recommend this product to a friend

after lugging around water for a few months i decided to get this along with a large storage container to relieve myself of water duties every morning. works great ! only have to top off the container once a week !

Once it's going it's great!By Terrieon 1/11/2013

Terrie would recommend this product to a friend

I have to come back and review again only b/c I gave it a 3 getting frustrated with the set up. The instructions are more for someone familiar with ATO's..not me.. this is my very 1st one. I finally found a forum 3reef that someone had posted full details with pics and was able to get mine going. Had I had any knowledge at all about what I was doing this would have been a 5 minute setup! Now I know, it's done, wow it's simple!!

It is not even letting and 1/8 of the water out before it tops it off... This I like!!! I pray for longevity for this price :)

???By Terrieon 1/10/2013

Terrie would recommend this product to a friend

I have to say I can't even give this item a rating yet. I received it a couple days ago and looked at it, put it back in the box and read the instructions. I took it out again and my head is spinning. Again today I took it out and my head is spinning. I'm trying to see the dark picture examples, I've read and read the instructions 10 times. For someone who has NEVER had an ATO of any type I chose this b/c of the good ratings and being BRS recommended. I figured I'd just spend the $ the first time instead of being someone who went less inexpensive and regretted it. However, like I said I've NEVER had an ATO of any type.... THIS THING NEEDS REAL INSTRUCTIONS FOR INSTALLATION!! I don't know what the parts are called so reading the long drawn out instructions isn't helping, the pics are too dark, and I can't find anything on the web!

Frustrated!

Great until it failedBy Guyon 1/8/2013

Guy wouldn't recommend this product to a friend

My Tunze 3155 is almost 4 yrs old, but just recently failed. After a short while it stops working and the TOO HIGH led is on while the TOO LOW led is flashing. I have to cycle power to reset it but it faults again shortly after the reset, no matter if the water level is good ( green led on) or low. I communicated with Tunze and the controller needs to be replaced. I find it difficult to have to pay for a complete controller unit (including sesors) just to replace the controller. Very expensive, almost the price of a new 3155. Plus I find this is not a rare occurance - easy to find others with same issue on the web. A super nice unit when it works, just too expensive to my taste.

COULD NOT LIVE WITHOUT IT!!!By Sherrion 1/8/2013

Sherri would recommend this product to a friend

I have never owned an ATO, but this has to be one of the best. I have no complaints whatsoever. I would recommend to everyone who runs saltwater tanks. Worth every penny and would repurchase again if needed.

It's worth the money...By gmastr85on 1/6/2013

gmastr85 would recommend this product to a friend

I can't compare this to other top off systems because this is my first, but I have zero complaints about this one. It comes with everything you need. The instructions are pretty easy to understand, and you can be setup and running fairly quickly. From opening the product to the small amount of assembling and reading the instructions, to filling your top off bucket and hooking the system up, you can be setup and running easily in under an hour. It even has a backup sensor on it incase the electric eye fails. You can't go wrong with this system. Pay the extra money and get this! Your system stability is well worth the price!

Great ProductBy Roberton 12/30/2012

Robert would recommend this product to a friend

I love this, water level and salinity stay at a constant, and the water level sensor is much more reliable then a float...

Just buy itBy Timon 12/24/2012

Tim would recommend this product to a friend

If you're wondering whether this thing is worth it...the answer is yes. After 7+ years of daily top-offs and getting neighbors to come in when we're away, I finally decided to get the osmolator. Wish I had done it years ago. Works as advertised.

Accurate when it worksBy Ryanon 12/22/2012

Ryan would recommend this product to a friend

I have had this since February of 2012 and have problems with it monthly if not a few times a month. When it doesn't stop working it keeps the level and salinity in my aquarium perfect. However, it continues to stop pumping water and the level will drop too much. I will then have to unplug the unit in order to reset it. I have contacted tunze about this and they have told me to check the contacts to make sure they are clean. They always are. Have yet to remedy the problem. If the unit would continue to operate constantly I would be giving the review 5 stars.